Mechanical Properties and Microstructure of Lightweight Aggregate Concrete Incorporating Basalt Fiber

Basalt fiber (BF) can notably improve the mechanical properties of lightweight aggregate concrete (LWAC) through its crack-bridging and pull-out mechanisms, making it suitable for application in super high-rise buildings and large-span structures. This study assesses the influence of BF contents of 0%, 0.1%, 0.3%, 0.5%, and 0.7% (relative to the weight of cementitious materials) on the workability, mechanical properties, and microstructure of LWAC. The results showed that adding BF to LWAC can moderately weaken the slump, significantly enhance the mechanical properties, and lead to a maximum increase in specific strength of 7.3%. Compared with LWAC without BF, the maximum increases in compressive strength, flexural strength, and elastic modulus of LWAC with BF at 28 days were 24.7%, 33.9%, and 38.57%, respectively. In the microstructure, BF can connect the cracks in the internal structure of concrete, which is an important factor to consider when choosing a fiber to improve the mechanical properties of concrete. These conclusions provide a reference point for improving the mechanical properties of LWAC.